No cooling limit

Multiple changes:

• Remove the Newton cooling scheme from the main cooling track.
• Fix the cooling from Iron.
• Do not set a maximal du/dt taking into account the increase in time-step size.
• Check the entropy floor in the drift and kick.
• Recompute the pressure and sound-speed after the floor has been applied.

doc/Doxyfile.in

@@ -811,7 +811,7 @@ RECURSIVE              = NO
 # Note that relative paths are relative to the directory from which doxygen is
 # run.
 
-EXCLUDE                =
+EXCLUDE                = @top_srcdir@/src/cooling/EAGLE/newton_cooling.c
 
 # The EXCLUDE_SYMLINKS tag can be used to select whether or not files or
 # directories that are symbolic links (a Unix file system feature) are excluded